1. Field of the Invention
The present disclosure relates to a perpendicular magnetic recording head that records information by applying a perpendicular magnetic field to a recording medium.
2. Description of the Related Art
As is widely known, a perpendicular magnetic recording head has a main magnetic pole layer, a return path layer, and a coil layer that provides a recording magnetic field to the main magnetic pole layer and the return path layer. The main magnetic pole layer and the return path layer are laminated with a nonmagnetic layer therebetween and form a surface that opposes a recording medium (hereinafter this surface is referred to as “recording medium-opposing surface”). The area of the main magnetic pole layer exposed to the recording medium-opposing surface is sufficiently smaller than the area of the return path layer exposed to the recording medium-opposing surface. The main magnetic pole layer is magnetically coupled to the return path layer at the side remote from the recording medium-opposing surface in the height direction. The main magnetic pole layer includes a pole straight part exposed to the recording medium-opposing surface and a flared part that connects to the back end of the pole straight part in the height direction. With this arrangement, a strong magnetic field can be applied to a local part of the recording medium. Once electricity is supplied to the coil layer, a recording magnetic field is induced between the main magnetic pole layer and the return path layer. The induced recording magnetic field enters a hard film of the recording medium in a perpendicular fashion from the front end surface of the main magnetic pole layer exposed to the recording medium-opposing surface. The recording magnetic field passes through a soft film of the recording medium and returns to the return path layer to thereby complete magnetic recording on the recording medium in the portion that opposes the main magnetic pole layer.
According to a proposal regarding a perpendicular magnetic recording head, the pole straight part (the portion that is exposed to the recording medium-opposing surface) of the main magnetic pole layer formed on the nonmagnetic layer is rendered to have a trapezoidal shape (bevel shape) that is narrowed at the nonmagnetic insulating layer side when viewed from the recording medium-opposing surface side. This is to increase the recording density and to prevent the generation of fringing at the time of skew. A perpendicular magnetic recording head having such a trapezoidal pole straight part is disclosed in Japanese Unexamined Patent Application Publication Nos. 2002-197611 and 2003-242608. In a perpendicular magnetic recording head, however, when a magnetic domain of the main magnetic pole layer and an auxiliary yoke layer is oriented perpendicular to the recording medium in a state that a recording current does not flow, a phenomenon known as the pole lockup is caused, erasing data recorded on the recording medium. According to a proposal regarding a method of preventing such a pole lockup phenomenon, a surface of a pole tip of the main magnetic pole layer on a trailing side is rendered asymmetrical with respect to the track center. A pole lockup preventing method is disclosed in Japanese Unexamined Patent Application Publication No. 2006-323899.
However, an asymmetrical pole tip can yield an uneven distribution of magnetic filed intensity with respect to the track center.